On Tue, 1 Apr 2014 15:04:01 +0100 Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
> On Tue, Apr 01, 2014 at 12:38:51PM +0100, Russell King - ARM Linux wrote:
> > Consider what happens when bio_alloc_pages() fails. j starts off as one
> > for non-recovery operations, and we enter the loop to allocate the pages.
> > j is post-decremented to zero. So, bio = r1_bio->bios[0].
> >
> > bio_alloc_pages(bio) fails, we jump to out_free_bio. The first thing
> > that does is increment j, so we free from r1_bio->bios[1] up to the
> > number of raid disks, leaving r1_bio->bios[0] leaked as the r1_bio is
> > then freed.
>
> Neil,
>
> Can you please review commit a07876064a0b7 (block: Add bio_alloc_pages)
> which seems to have introduced this bug - it seems to have gone in during
> the v3.10 merge window, and looks like it was never reviewed from the
> attributations on the commit.
>
> The commit message is brief, and inadequately describes the functional
> change that the patch has - we go from "get up to RESYNC_PAGES into the
> bio's io_vec" to "get all RESYNC_PAGES or fail completely".
>
> Not withstanding the breakage of the error cleanup paths, is this an
> acceptable change of behaviour here?
>
> Thanks.
>
Hi Russell,
thanks for finding that bug! - I'm sure I looked at that code, but obviously
missed the problem :-(
Below is the fix that I plan to submit. It is slightly different from yours
but should achieve the same effect. If you could confirm that it looks good
to you I would appreciate it.
Thanks,
NeilBrown
From 72dce88eee7259d65c6eba10c2e0beff357f713b Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Thu, 3 Apr 2014 10:19:12 +1100
Subject: [PATCH] md/raid1: r1buf_pool_alloc: free allocate pages when
subsequent allocation fails.
When performing a user-request check/repair (MD_RECOVERY_REQUEST is set)
on a raid1, we allocate multiple bios each with their own set of pages.
If the page allocations for one bio fails, we currently do *not* free
the pages allocated for the previous bios, nor do we free the bio itself.
This patch frees all the already-allocate pages, and makes sure that
all the bios are freed as well.
This bug can cause a memory leak which can ultimately OOM a machine.
It was introduced in 3.10-rc1.
Fixes: a07876064a0b73ab5ef1ebcf14b1cf0231c07858
Cc: Kent Overstreet <koverstreet@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx (3.10+)
Reported-by: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 4a6ca1cb2e78..56e24c072b62 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -97,6 +97,7 @@ static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data)
struct pool_info *pi = data;
struct r1bio *r1_bio;
struct bio *bio;
+ int need_pages;
int i, j;
r1_bio = r1bio_pool_alloc(gfp_flags, pi);
@@ -119,15 +120,15 @@ static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data)
* RESYNC_PAGES for each bio.
*/
if (test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery))
- j = pi->raid_disks;
+ need_pages = pi->raid_disks;
else
- j = 1;
- while(j--) {
+ need_pages = 1;
+ for (j = 0; j < need_pages; j++) {
bio = r1_bio->bios[j];
bio->bi_vcnt = RESYNC_PAGES;
if (bio_alloc_pages(bio, gfp_flags))
- goto out_free_bio;
+ goto out_free_pages;
}
/* If not user-requests, copy the page pointers to all bios */
if (!test_bit(MD_RECOVERY_REQUESTED, &pi->mddev->recovery)) {
@@ -141,6 +142,14 @@ static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data)
return r1_bio;
+out_free_pages:
+ while (--j >= 0) {
+ struct bio_vec *bv;
+
+ bio_for_each_segment_all(bv, r1_bio->bios[j], i)
+ __free_page(bv->bv_page);
+ }
+
out_free_bio:
while (++j < pi->raid_disks)
bio_put(r1_bio->bios[j]);
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